A bell is used at depths greater than 220 fsw or when the dive involves inwater decompression time of greater than 120 minutes, except when heavy gear is worn or when diving in physically confining spaces; or

1910.426(b)(1)(ii)

A closed bell is used at depths greater than 300 fsw, except when diving is conducted in physically confining spaces.

1910.426(c)

Procedures.

1910.426(c)(1)

A separate dive team member shall tend each diver in the water.

1910.426(c)(2)

A standby diver shall be available while a diver is in the water.

1910.426(c)(3)

A diver shall be stationed at the underwater point of entry when diving is conducted in enclosed or physically confining spaces.

1910.426(c)(4)

Each diving operation shall have a primary breathing gas supply sufficient to support divers for the duration of the planned dive including decompression.